Dc-link voltage control of full power converter for wind generator operating in weak grid systems

In this paper, permanent magnet wind generator with full power converter is investigated in weak grid systems, where the dc-link voltage needs to be controlled from the generator side instead of grid side. When wind power takes a large portion of grid power, it needs to help grid to regulate the voltage and frequency. To achieve this, a variable step search algorithm based on the derivation of the electro-mechanical dynamic model describing the wind turbine is proposed, which enables the wind generator output power to match the load power, thus keeping the dc-link voltage regulated. Based on the non-linearity and different slopes of wind power curve, the controller is designed specifically for different sectors. A back-EMF observer based sensor-less generator control is adopted here to regulate the generator speed. Simulation is built up with a 10 kW wind power generator system and a reduced-scale 1.5 kW system experiment is also carried out in the condition of load power step change and wind speed change. Both simulation and experimental results validate the effectiveness of the proposed control scheme, where the dc-link voltage can be kept stable by adjusting the wind generator speed.